Moissanite has a hardness of 9.5, which makes it nearly as hard as diamond, and also has needle-like, sometimes even string-like inclusions. What differentiates moissanite and diamonds is not only the chemical structure, but also the fire and brilliance.
While diamonds are beautiful and sparkly, moissanite is even more so. Moissanite is 10% more brilliant than diamonds, and more brilliant than any other gemstone, because of its refractive index of 2.65-2.69. Plus, moissanite's "fire," or the pretty flashes of color it sends out, is 2.4 times greater than a diamond's of the same cut! Moissanite is not graded on the same system as diamonds, using the "Four Cs", but moissanite stones are considered VS (very slight inclusion) and are sold by the carat weight.
Moissanite is also considered a "green" gem, and, no I don't mean that it's been buried in radium bromide powder. Instead, because moissanite is a created gem, the impact to the environment is much less than a mined gem. It is also considered a "fair trade" gem, for those who are concerned with the diamond trade.
Moissanite is spiritually neutral and isn't considered to have any metaphysical properties. Although, given the fire and brilliance of the stone, it sure does make a girl happy, and at 1/3 the cost of diamonds, it makes a guy happy too! So, while diamonds may be a girl's best friend, moissanite is a more affordable and sometimes even more beautiful alternative.